Indirect Environmental Effects of Dikes on Estuarine Tidal Channels: Thinking Outside of the Dike for Habitat Restoration and Monitoring
TL;DR: In this article, the authors analyzed historical photos of the Skagit River delta marshes (Washington, U.S.) and compared changes in estuarine marsh and tidal channel surface area from 1956-2000 in the Wiley Slough area of the South Fork Skagits delta, and from 1937-2000 on the North Fork delta.
Abstract: While the most obvious effects of dike construction and marsh conversion are those affecting the con- verted land (direct or intended effects), less immediately apparent effects also occur seaward of dikes (indirect or unintended effects). I analyzed historical photos of the Skagit River delta marshes (Washington, U.S.) and compared changes in estuarine marsh and tidal channel surface area from 1956-2000 in the Wiley Slough area of the South Fork Skagit delta, and from 1937-2000 in the North Fork delta. Dike construction in the late 1950s caused the loss of 80 ha of estuarine marsh and 6.7 ha of tidal channel landward of the Wiley Slough dikes. A greater amount of tidal channel surface area, 9.6 ha, was lost seaward of the dikes. Similar losses were observed for two smaller North Fork tidal channel systems. Tidal channels far from dikes did not show comparable changes in channel surface area. These results are consistent with hydraulic geometry theory, which predicts that diking reduces tidal flushing in the undiked channel remnants and this results in sedimentation. Dikes may have significant seaward effects on plants and animals associated with tidal channel habitat. Another likely indirect dike effect is decreased sinuosity in a distributary channel of the South Fork Skagit River adjacent to and downstream of the Wiley Slough dikes, compared to distributary channels upstream or distant from the dikes. Loss of floodplain area to diking and marsh conversion prevents flood energy dissipation over the marsh surface. The distributary channel has responded to greater flood energy by increasing mean channel width and decreasing sinuosity. Restoration of diked areas should consider historic habitat loss seaward of dikes, as well as possible benefits to these areas from dike breaching or removal. Habitat restoration by breaching or removal of dikes should be monitored in areas directly affected by dikes, areas indirectly affected, and distinct reference areas.
Citations
More filters
TL;DR: A literature review as discussed by the authors gives an overview of a broad range of management measures that are, or can be, applied for estuarine management, including measures to change hydrology, morphology, habitat, and water and sediment quality.
47 citations
TL;DR: In this article, the interactions between flow, vegetation, and sediment documented in inland and tidal marshes, chalk and Coastal Plain streams, large river floodplains, and deltas are reviewed and classified into feedback processes occurring over a range of five spatiotemporal scales.
46 citations
TL;DR: In this paper, the authors examined how local and regional-scale environmental drivers affect patterns of abundance and recruitment in two abundant and ecologically significant forage fishes (Pacific herring Clupea pallasi and surf smelt Hypomesus pretiosus) in the Skagit River estuary (Puget Sound, Wash-ington, USA).
Abstract: We examined how local- and regional-scale environmental drivers affect patterns ofabundance and recruitment in 2 abundant and ecologically significant forage fishes (Pacific herring Clupea pallasi and surf smelt Hypomesus pretiosus) in the Skagit River estuary (Puget Sound, Wash-ington, USA). We identified associations between survey catch rates and environmental conditions at2 scales: within-season distributional shifts in response to local environmental conditions, and inter-annual patterns of relative year class strength related to both local- and regional-scale drivers. Usingmonthly data that spanned a 9 yr period, we found that a small proportion (<2%) of the total deviancein catch rates for both species was related to within-estuary variation in surface water temperatureand salinity but that a larger fraction (7 and 12% for Pacific herring and surf smelt, respectively) wasexplained by interannual variation in recruitment strength. Annual abundance indices for both spe-cies were uncorrelated with cumulative river discharge and regional sea surface temperature butpositively correlated with an index of cumulative coastal upwelling, suggesting a linkage betweenregional-scale environmental conditions and age-0 recruitment. Moreover, our annual age-0 Pacificherring time series was positively correlated with a similar time series from the Strait of Georgia(~100 km north), further suggesting that age-0 recruitment in these populations is synchronized byregional upwelling as opposed to estuary-specific environmental forcing related to river flows. Thepresent study isolates a potential key process governing age-0 forage fish abundance in this systemand highlights the importance of simultaneously evaluating patterns of variability across multiplespatiotemporal scales in order to identify the primary pathways through which climate may impactestuarine populations.KEY WORDS: Puget Sound · Pacific herring · Surf smelt · Deviance partitioning · Upwelling ·Fish recruitment
45 citations
TL;DR: In this article, the authors describe a contrasting depositional model for blind tidal channel origin and development in the Skagit River delta, Washington, USA, showing that as sediments accumulated at the river mouth, vegetation colonization created marsh islands that splintered the river into distributaries, and the marsh islands coalesced when intervening distributary channels gradually narrowed and finally closed at the upstream end to form a blind channel, or at mid-length to form two blind channels.
Abstract: The origin and growth of blind tidal channels is generally considered to be an erosional process. This paper describes a contrasting depositional model for blind tidal channel origin and development in the Skagit River delta, Washington, USA. Chronological sequences of historical maps and photos spanning the last century show that as sediments accumulated at the river mouth, vegetation colonization created marsh islands that splintered the river into distributaries. The marsh islands coalesced when intervening distributary channels gradually narrowed and finally closed at the upstream end to form a blind tidal channel, or at mid-length to form two blind tidal channels. Channel closure was probably often mediated through gradient reduction associated with marsh progradation and channel lengthening, coupled with large woody debris blockages. Blind tidal channel evolution from distributaries was common in the Skagit marshes from 1889 to the present, and it can account for the origin of very small modern blind tidal channels. The smallest observed distributary-derived modern blind tidal channels have mean widths of 0·3 m, at the resolution limit of the modern orthophotographs. While channel initiation and persistence are similar processes in erosional systems, they are different processes in this depositional model. Once a channel is obstructed and isolated from distributary flow, only tidal flow remains and channel persistence becomes a function of tidal prism and tidal or wind/wave erosion. In rapidly prograding systems like the Skagit, blind tidal channel networks are probably inherited from the antecedent distributary network. Examination of large-scale channel network geometry of such systems should therefore consider distributaries and blind tidal channels part of a common channel network and not entirely distinct elements of the system. Finally, managers of tidal habitat restoration projects generally assume an erosional model of tidal channel development. However, under circumstances conducive to progradation, depositional channel development may prevail instead. Copyright © 2006 John Wiley & Sons, Ltd.
40 citations
Cites background from "Indirect Environmental Effects of D..."
...Insufficient tidal prism and competition between channels for drainage probably causes tidally transported sediments to accumulate and fill the channels (Hood, 2004)....
[...]
...Insufficient tidal prism and competition between channels for drainage probably causes tidally transported sediments to accumulate and fill the channels ( Hood, 2004 )....
[...]
TL;DR: In this paper, the scaling relationship between marsh island surface area and various metrics of the set of tidal channels draining each island was used to estimate the channel size and complexity in the Skagit Delta Marsh.
Abstract: [1] Hydraulic geometry and related analyses are often used to investigate tidal channel geometry and evolution and inform marsh restoration. An alternative approach is presented that avoids calculating tidal prism and allows analysis of additional channel metrics. It relies on scaling relationships between marsh island surface area and various metrics of the set of tidal channels draining each island. In the Skagit Delta marshes (Washington, United States), total channel surface area and length and surface area of the largest channel draining an island scaled disproportionately with island area, suggesting restoration of a 100-ha site would be preferable to restoration of 10 separate 10-ha sites to maximize channel length and area. A model of channel formation through random island conglomeration replicated observed scaling patterns, linking channel scaling to blind channel evolution from river distributaries. Channel size and complexity varied spatially, with significant deficits in an eroding marsh isolated from river distributaries and riverine sediments.
39 citations
References
More filters
Book•
01 Jan 1982
TL;DR: This book is a blend of erudition, popularization, and exposition, and the illustrations include many superb examples of computer graphics that are works of art in their own right.
Abstract: "...a blend of erudition (fascinating and sometimes obscure historical minutiae abound), popularization (mathematical rigor is relegated to appendices) and exposition (the reader need have little knowledge of the fields involved) ...and the illustrations include many superb examples of computer graphics that are works of art in their own right." Nature
24,199 citations
01 Jul 1984
TL;DR: A blend of erudition (fascinating and sometimes obscure historical minutiae abound), popularization (mathematical rigor is relegated to appendices) and exposition (the reader need have little knowledge of the fields involved) is presented in this article.
Abstract: "...a blend of erudition (fascinating and sometimes obscure historical minutiae abound), popularization (mathematical rigor is relegated to appendices) and exposition (the reader need have little knowledge of the fields involved) ...and the illustrations include many superb examples of computer graphics that are works of art in their own right." Nature
7,560 citations
"Indirect Environmental Effects of D..." refers background in this paper
...Tidal channel allometry follows from a more general fractal theory of landforms (RodriguezIturbe and Rinaldo 1997), and the scaling of perimeter with surface area is a common reflection of landform fractal geometry (Mandelbrot 1983; Sugihara and May 1990)....
[...]
3,626 citations
Book•
01 Jan 1995
TL;DR: Fluvial processes in geomorphology, Fluvial Processes in Geomorphology as discussed by the authors, fluvial processes and geomorphological processes in the field of geology.
Abstract: Fluvial processes in geomorphology , Fluvial processes in geomorphology , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
1,781 citations
"Indirect Environmental Effects of D..." refers background in this paper
...Greater adjustment in width relative to depth with changing discharge is consistent with hydraulic geometry theory (Leopold et al. 1964)....
[...]
...Because high sinuosity is associated with small channel width relative to depth (Leopold et al. 1964), the observed correlation between changes in sinuosity and in mean channel width suggests that distributary channel widths changed to a greater degree than channel depths....
[...]
...As a final error check, meander bends in tidal channels were examined at scales ranging from 1:1,000 to 1:10,000 to determine whether erosion had occurred in the cut banks of the meanders and sediment deposition at the point bars, in accord with theoretical expectations (Leopold et al. 1964)....
[...]
...Sinuosity was the ratio of sinuous length to straight length (Leopold et al. 1964)....
[...]